80% of ICPs nodes are held by just 8 separate node provider entities

[icarus]

Because the current boundary nodes are Dfinity controlled and, as implemented now, they cannot be run in a trustless manner. Dfinity engineering team is building a redesigned boundary server model so that independent node providers can apply to run new API Boundary Nodes which are secured from interference in a similar manner to the IC Replica Nodes.
ETA is later this year IIUC, then decentralised boundary node services will become a reality.

See this whole thread for more information:

@rbirkner

The boundary nodes will be split into two parts: the API Boundary Nodes that serve only the Internet Computer API endpoints (query, call, read state, status) and the Gateways (currently only the HTTP Gateways) that map between a protocol and the Internet Computer API (e.g., in the case of HTTP Gateways between HTTP(S) and API calls such that browsers can directly access dapps hosted on-chain). Anyone is free to run any gateway.